Field of the Invention
The present invention relates to a charger for charging a battery pack of a rechargeable electric power tool.
Description of the Related Art
A battery pack serving as a power source for a rechargeable electric power tool such as a screw-tightening tool or a cutting tool can be removed from the electric power tool and charged using a dedicated charger. In most cases, an alternating current of 100 volts is used for charging. A lithium ion battery having DC 18 volts, for example, can be charged by the charger.
Further, there is a type of charger that can be attached to a belt round a user's waist. This type of charger is electrically connected to a tool main body via an electric cord. A separate battery pack from a battery pack mounted to the tool main body is attached to this type of charger. The separate battery pack can charge the battery pack mounted to the tool main body via the electric cord.
Various improvements have been made for these types of charger. For example, Japanese Laid-Open Patent Publication No. 2012-95417 discloses a charger in which its water-resistant property can be improved by sealing the inside of the charger.
A charging circuit, for controlling the operation of charging, is housed inside the charger. The charging circuit may include a transformer and switching elements with a heat sink, and these elements may become heat generation sources. Accordingly, when the case of the charger is configured to seal in order to improve its water-resistant property, heat generated by the charging circuit is likely to accumulate inside the case. Normally, the heat generated by the charging circuit is transferred upwards by convection, and thus the upper side of the case is likely to be locally heated. If a user happens to touch these areas which are locally heated, the user may find it quite uncomfortable or even impossible to hold and carry the charger. Further, the user may mistakenly believe that something is wrong with the charger.
Thus, there is a need to prevent surfaces of the case of the charger from being locally heated.